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[PATCH] PCI: fix race with pci_walk_bus and pci_destroy_dev
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pci_walk_bus has a race with pci_destroy_dev. When cb is called
in pci_walk_bus, pci_destroy_dev might unlink the dev pointed by next.
Later on in the next loop, pointer next becomes NULL and cause
kernel panic.

Below patch against 2.6.17-rc4 fixes it by changing pci_bus_lock (spin_lock)
to pci_bus_sem (rw_semaphore).

Signed-off-by: Zhang Yanmin <yanmin.zhang@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
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Zhang Yanmin authored and Greg Kroah-Hartman committed Jun 21, 2006
1 parent 733a7fe commit d71374d
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Showing 5 changed files with 41 additions and 43 deletions.
21 changes: 9 additions & 12 deletions drivers/pci/bus.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -81,9 +81,9 @@ void __devinit pci_bus_add_device(struct pci_dev *dev)
{
device_add(&dev->dev);

spin_lock(&pci_bus_lock);
down_write(&pci_bus_sem);
list_add_tail(&dev->global_list, &pci_devices);
spin_unlock(&pci_bus_lock);
up_write(&pci_bus_sem);

pci_proc_attach_device(dev);
pci_create_sysfs_dev_files(dev);
Expand Down Expand Up @@ -125,10 +125,10 @@ void __devinit pci_bus_add_devices(struct pci_bus *bus)
*/
if (dev->subordinate) {
if (list_empty(&dev->subordinate->node)) {
spin_lock(&pci_bus_lock);
down_write(&pci_bus_sem);
list_add_tail(&dev->subordinate->node,
&dev->bus->children);
spin_unlock(&pci_bus_lock);
up_write(&pci_bus_sem);
}
pci_bus_add_devices(dev->subordinate);

Expand Down Expand Up @@ -168,7 +168,7 @@ void pci_walk_bus(struct pci_bus *top, void (*cb)(struct pci_dev *, void *),
struct list_head *next;

bus = top;
spin_lock(&pci_bus_lock);
down_read(&pci_bus_sem);
next = top->devices.next;
for (;;) {
if (next == &bus->devices) {
Expand All @@ -180,22 +180,19 @@ void pci_walk_bus(struct pci_bus *top, void (*cb)(struct pci_dev *, void *),
continue;
}
dev = list_entry(next, struct pci_dev, bus_list);
pci_dev_get(dev);
if (dev->subordinate) {
/* this is a pci-pci bridge, do its devices next */
next = dev->subordinate->devices.next;
bus = dev->subordinate;
} else
next = dev->bus_list.next;
spin_unlock(&pci_bus_lock);

/* Run device routines with the bus unlocked */
/* Run device routines with the device locked */
down(&dev->dev.sem);
cb(dev, userdata);

spin_lock(&pci_bus_lock);
pci_dev_put(dev);
up(&dev->dev.sem);
}
spin_unlock(&pci_bus_lock);
up_read(&pci_bus_sem);
}
EXPORT_SYMBOL_GPL(pci_walk_bus);

Expand Down
2 changes: 1 addition & 1 deletion drivers/pci/pci.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -40,7 +40,7 @@ extern int pci_bus_find_capability (struct pci_bus *bus, unsigned int devfn, int
extern void pci_remove_legacy_files(struct pci_bus *bus);

/* Lock for read/write access to pci device and bus lists */
extern spinlock_t pci_bus_lock;
extern struct rw_semaphore pci_bus_sem;

#ifdef CONFIG_X86_IO_APIC
extern int pci_msi_quirk;
Expand Down
17 changes: 9 additions & 8 deletions drivers/pci/probe.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -383,9 +383,9 @@ struct pci_bus * __devinit pci_add_new_bus(struct pci_bus *parent, struct pci_de

child = pci_alloc_child_bus(parent, dev, busnr);
if (child) {
spin_lock(&pci_bus_lock);
down_write(&pci_bus_sem);
list_add_tail(&child->node, &parent->children);
spin_unlock(&pci_bus_lock);
up_write(&pci_bus_sem);
}
return child;
}
Expand Down Expand Up @@ -844,9 +844,9 @@ void __devinit pci_device_add(struct pci_dev *dev, struct pci_bus *bus)
* and the bus list for fixup functions, etc.
*/
INIT_LIST_HEAD(&dev->global_list);
spin_lock(&pci_bus_lock);
down_write(&pci_bus_sem);
list_add_tail(&dev->bus_list, &bus->devices);
spin_unlock(&pci_bus_lock);
up_write(&pci_bus_sem);
}

struct pci_dev * __devinit
Expand Down Expand Up @@ -981,9 +981,10 @@ struct pci_bus * __devinit pci_create_bus(struct device *parent,
pr_debug("PCI: Bus %04x:%02x already known\n", pci_domain_nr(b), bus);
goto err_out;
}
spin_lock(&pci_bus_lock);

down_write(&pci_bus_sem);
list_add_tail(&b->node, &pci_root_buses);
spin_unlock(&pci_bus_lock);
up_write(&pci_bus_sem);

memset(dev, 0, sizeof(*dev));
dev->parent = parent;
Expand Down Expand Up @@ -1023,9 +1024,9 @@ struct pci_bus * __devinit pci_create_bus(struct device *parent,
class_dev_reg_err:
device_unregister(dev);
dev_reg_err:
spin_lock(&pci_bus_lock);
down_write(&pci_bus_sem);
list_del(&b->node);
spin_unlock(&pci_bus_lock);
up_write(&pci_bus_sem);
err_out:
kfree(dev);
kfree(b);
Expand Down
12 changes: 6 additions & 6 deletions drivers/pci/remove.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -22,18 +22,18 @@ static void pci_destroy_dev(struct pci_dev *dev)
pci_proc_detach_device(dev);
pci_remove_sysfs_dev_files(dev);
device_unregister(&dev->dev);
spin_lock(&pci_bus_lock);
down_write(&pci_bus_sem);
list_del(&dev->global_list);
dev->global_list.next = dev->global_list.prev = NULL;
spin_unlock(&pci_bus_lock);
up_write(&pci_bus_sem);
}

/* Remove the device from the device lists, and prevent any further
* list accesses from this device */
spin_lock(&pci_bus_lock);
down_write(&pci_bus_sem);
list_del(&dev->bus_list);
dev->bus_list.next = dev->bus_list.prev = NULL;
spin_unlock(&pci_bus_lock);
up_write(&pci_bus_sem);

pci_free_resources(dev);
pci_dev_put(dev);
Expand Down Expand Up @@ -62,9 +62,9 @@ void pci_remove_bus(struct pci_bus *pci_bus)
{
pci_proc_detach_bus(pci_bus);

spin_lock(&pci_bus_lock);
down_write(&pci_bus_sem);
list_del(&pci_bus->node);
spin_unlock(&pci_bus_lock);
up_write(&pci_bus_sem);
pci_remove_legacy_files(pci_bus);
class_device_remove_file(&pci_bus->class_dev,
&class_device_attr_cpuaffinity);
Expand Down
32 changes: 16 additions & 16 deletions drivers/pci/search.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -13,7 +13,7 @@
#include <linux/interrupt.h>
#include "pci.h"

DEFINE_SPINLOCK(pci_bus_lock);
DECLARE_RWSEM(pci_bus_sem);

static struct pci_bus * __devinit
pci_do_find_bus(struct pci_bus* bus, unsigned char busnr)
Expand Down Expand Up @@ -72,11 +72,11 @@ pci_find_next_bus(const struct pci_bus *from)
struct pci_bus *b = NULL;

WARN_ON(in_interrupt());
spin_lock(&pci_bus_lock);
down_read(&pci_bus_sem);
n = from ? from->node.next : pci_root_buses.next;
if (n != &pci_root_buses)
b = pci_bus_b(n);
spin_unlock(&pci_bus_lock);
up_read(&pci_bus_sem);
return b;
}

Expand Down Expand Up @@ -124,7 +124,7 @@ struct pci_dev * pci_get_slot(struct pci_bus *bus, unsigned int devfn)
struct pci_dev *dev;

WARN_ON(in_interrupt());
spin_lock(&pci_bus_lock);
down_read(&pci_bus_sem);

list_for_each(tmp, &bus->devices) {
dev = pci_dev_b(tmp);
Expand All @@ -135,7 +135,7 @@ struct pci_dev * pci_get_slot(struct pci_bus *bus, unsigned int devfn)
dev = NULL;
out:
pci_dev_get(dev);
spin_unlock(&pci_bus_lock);
up_read(&pci_bus_sem);
return dev;
}

Expand Down Expand Up @@ -167,7 +167,7 @@ static struct pci_dev * pci_find_subsys(unsigned int vendor,
struct pci_dev *dev;

WARN_ON(in_interrupt());
spin_lock(&pci_bus_lock);
down_read(&pci_bus_sem);
n = from ? from->global_list.next : pci_devices.next;

while (n && (n != &pci_devices)) {
Expand All @@ -181,7 +181,7 @@ static struct pci_dev * pci_find_subsys(unsigned int vendor,
}
dev = NULL;
exit:
spin_unlock(&pci_bus_lock);
up_read(&pci_bus_sem);
return dev;
}

Expand Down Expand Up @@ -232,7 +232,7 @@ pci_get_subsys(unsigned int vendor, unsigned int device,
struct pci_dev *dev;

WARN_ON(in_interrupt());
spin_lock(&pci_bus_lock);
down_read(&pci_bus_sem);
n = from ? from->global_list.next : pci_devices.next;

while (n && (n != &pci_devices)) {
Expand All @@ -247,7 +247,7 @@ pci_get_subsys(unsigned int vendor, unsigned int device,
dev = NULL;
exit:
dev = pci_dev_get(dev);
spin_unlock(&pci_bus_lock);
up_read(&pci_bus_sem);
pci_dev_put(from);
return dev;
}
Expand Down Expand Up @@ -292,7 +292,7 @@ pci_find_device_reverse(unsigned int vendor, unsigned int device, const struct p
struct pci_dev *dev;

WARN_ON(in_interrupt());
spin_lock(&pci_bus_lock);
down_read(&pci_bus_sem);
n = from ? from->global_list.prev : pci_devices.prev;

while (n && (n != &pci_devices)) {
Expand All @@ -304,7 +304,7 @@ pci_find_device_reverse(unsigned int vendor, unsigned int device, const struct p
}
dev = NULL;
exit:
spin_unlock(&pci_bus_lock);
up_read(&pci_bus_sem);
return dev;
}

Expand All @@ -328,7 +328,7 @@ struct pci_dev *pci_get_class(unsigned int class, struct pci_dev *from)
struct pci_dev *dev;

WARN_ON(in_interrupt());
spin_lock(&pci_bus_lock);
down_read(&pci_bus_sem);
n = from ? from->global_list.next : pci_devices.next;

while (n && (n != &pci_devices)) {
Expand All @@ -340,7 +340,7 @@ struct pci_dev *pci_get_class(unsigned int class, struct pci_dev *from)
dev = NULL;
exit:
dev = pci_dev_get(dev);
spin_unlock(&pci_bus_lock);
up_read(&pci_bus_sem);
pci_dev_put(from);
return dev;
}
Expand All @@ -362,7 +362,7 @@ int pci_dev_present(const struct pci_device_id *ids)
int found = 0;

WARN_ON(in_interrupt());
spin_lock(&pci_bus_lock);
down_read(&pci_bus_sem);
while (ids->vendor || ids->subvendor || ids->class_mask) {
list_for_each_entry(dev, &pci_devices, global_list) {
if (pci_match_one_device(ids, dev)) {
Expand All @@ -372,8 +372,8 @@ int pci_dev_present(const struct pci_device_id *ids)
}
ids++;
}
exit:
spin_unlock(&pci_bus_lock);
exit:
up_read(&pci_bus_sem);
return found;
}
EXPORT_SYMBOL(pci_dev_present);
Expand Down

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